We are engaged in the study of the cells of the antibody-forming system. The work of the next year is directed toward a description of the spread of antibody in the local lymph node and the determination of the H-chain class during the rise and fall of both primary and recall responses in the rabbit. This will be done using two labels and fluorescence microscopy. We also intend to study the surface immunoglobulin and antigen-binding capacity of cultured cell lines.